This invention relates to vehicle lifting and towing apparatus and more particularly to apparatus of this type integrated into the bed of a towing vehicle and having a boom elevationally extendible at an incline and angularly adjustable for permitting attitude control of the boom regardless of its elevation.
Recent developments in the art of lifting and towing disabled vehicles by a towing vehicle have resulted in wheel lift devices which engage and lift the front or rear wheels of the disabled vehicle. Most of these known devices are of the type which may be attached to the rear of a towing vehicle and utilized in conjunction with conventional wrecker apparatus. As illustrated in Cannon, et al U.S. Pat. No. 4,451,193 assigned to the common assignee of the present invention, these devices are used in conjunction with the wrecker boom and winching apparatus. Another example of this type of device appears to be illustrated in Peterson U.S. Pat. No. 4,384,817. It is, however, desirable to combine the features of a wrecker and a wheel lift device. Examples of this are illustrated in Brown U.S. Pat. No. 4,473,334; Lind U.S. Pat. No. 4,473,237; Pigeon U.S. Pat. No. 3,924,763; German Auslegeschrift No. 26,08,523; and German Offenlegungsschraft No. 28,21,436.
An important criteria of such devices is that the wheel engaging apparatus be stored within the bed of the towing vehicle or as close to the tail board thereof as possible when the device is in the storage position.
The known current wheel lifts have a horizontally telescoping boom which either pivots about a stationary frame member or is attached to a parallelogram linkage which pivots about a stationary frame member. Another known method of boom control is to attach rollers to the boom and move it vertically and rearwardly on a track.
The ideal wheel lift is one in which minimum extension occurs so that in the storage condition the apparatus does not encumber the bed, thereby permitting recovery apparatus to be utilized on the same vehicle if desired. Additionally, the apparatus should be capable of retracting a towed vehicle closely to the tailboard to provide a weight distribution on the towing vehicle which overcomes the tendency of the front wheels lifting. Moreover, the ideal wheel lift apparatus should have a wheel engaging frame or carriage which can follow the contour of the road-bed even when on a slope, and permit the wheel engaging elements to dig in and get under the wheels of the vehicle to be towed even when, for example, there is snow on the road. Furtherfore, such apparatus should provide sufficient ground clearance between the towed vehicle even when a low slung vehicle is towed.